EPR, luminescence and IR studies of Mn activated ZnGa 2O 4 phosphor

Abstract

Electron paramagnetic resonance (EPR), luminescence and infrared spectra of Mn 2+ ions doped in zinc gallate (ZnGa 2O 4) powder phosphor have been studied. The EPR spectra have been recorded for zinc gallate phosphor doped with different concentrations of Mn 2+ ions. The EPR spectra exhibit characteristic spectrum of Mn 2+ ions ( S= I=5/2) with a sextet hyperfine pattern, centered at g eff=2.00. At higher concentrations of Mn 2+ ions, the intensity of the resonance signals decreases. The number of spins participating in the resonance has been measured as a function of temperature and the activation energy ( E a) is calculated. The EPR spectra of ZnGa 2O 4: Mn 2+ have been recorded at various temperatures. From the EPR data, the paramagnetic susceptibility ( χ) at various temperatures, the Curie constant ( C) and the Curie temperature ( θ) have been evaluated. The emission spectrum of ZnGa 2O 4: Mn 2+ (0.08 mol%) exhibits two bands centered at 468 and 502 nm. The band observed at 502 nm is attributed to 4T 1→ 6A 1 transition of Mn 2+ ions. The band observed at 468 nm is attributed to the trap-state transitions. The excitation spectrum exhibits two bands centered at 228 and 280 nm. The strong band at 228 nm is attributed to host-lattice absorption and the weak band at 280 nm is attributed to the charge-transfer absorption or d 5→d 4s transition band. The observed bands in the FT-IR spectrum are assigned to the stretching vibrations of M–O groups at octahedral and tetrahedral sites.